Hydraulic braking system



June 2,l 1942, GQR.- e.; GATES' mamma -BRAKING SYSTEM '2 SheetsSheet /1A @EET Filed larch 9, 1939 f lar/ffl INVENTOR. Geoffrey RG. Gates BYoff/w .Q

June 2,; 1942. G. R. G. GATES 2,284,974

HYDRAULIC BRAKING SYSTEM Filed March 9. 1939 2 Sheets-Sheet 2//////////////7//`/ il?? A ///////)V///7/MM i 7 :uw

INVEN TOR.

Geoffrzg l2. G. Gares.

BY Q @Q14 ATTORNEY.

'Patented June 2, 1942 mimmo ammo SYSTEMv Geoffrey Robert Greenber'ghGates, London, England, assign'or to Automotive Products ,Com-

pany Limited, London, England Appiicatin'Ml'dh 9, 1939, Serial N0.260,830 l .InGl'eat Britain March 12, 1938 s claims. '(cl. so-54.5)

'I'his invention relates to master cylinder units for liquid pressurepower transmission systems of the kind in which two or more motorv unitsor sets of units are operated by pressure generated in'mutually isolatedpressure spaces in a single I, master cylinder unit having a mainpistonl operated .by external means, and a oating piston or iloatingpistons separating the' pressure spaces.

vehicle, having liquid pressure operated brakes on all four wheels, thebrakes being diagrammatically indicated in Figure 1 at A, A, A1, A1,with motor cylinders B, B, B1, B1, by which the shoes are expanded. 'Ihemaster cylinder unit is operated by a pedal `C and rod D.

The master cylinder unit comprises a casting a I having formed in itslower part a main bore The object of the invention is to provide an'improved construction o1' a cylinder of this kind.

According to the invention regarded broadly,

the master cylinder unit comprises a main cylinder bore, one auxiliarybore in parallel sideby-side relation to the-main bore, an externallyoperable piston in the main bore, a oating piston in the auxiliary bore,the main piston and the floating piston delivering liquid each to one ormore motor units, and the floating piston being operated by pressureproduced by vthe main piston, the said pressure acting directly on therear face of the operated piston. Thus, according to the invention, amaster lcylinder unit is provided which works in the manner of a tandemmaster cylinder to supplya number of mutually'independent branches of aliquid pressure system, the cylinder in this case being of U-shape, oneof the limbs to accommodate the main piston, and the other-toaccommodate a noating piston. A rocker is preferably mounted on the endof the cylinder unit'between the auxiliary bore and the'bore containingthe piston bywhich liquid pressure is supplied to actuate the floatingpiston in said auxiliary bore. said pressure supplying piston engagingthe rocker on moving beyond its normal stroke, and transmitting movementmechan- 2 and an auxiliary bore 3 in parallel sideby-side relation. Themain bore is open at both ends, the auxiliary bore being open at one endonly and closed at the other end except for a passage 4 suitablythreaded to receive a pipe union.

rAbove the cylinder bores 2 and -3 isa reservoir space 5 divided intotwo sections 6 and I to provide an independent liquid supply for each ofthe two cylinder bores, the reservoir space, being closed by a top plate`8 fitted with a detachable nlling cap I I. On the end of the cylinderunit at which both bores 2-and l3 are open is iitted a cover .plate I2having in its face which abuts against the end of the master cylinderunit a cavity 'I3 forming a connecting passage between the $0 the rearend of the piston, the thrust rod being two bores. Connected to thiscavity I3 by a passage II is an outwardly directed recess I5 into whichis threaded a plug I6 adapted to receive a pipe union.

In the main bore 2 isiltted a piston I8 operable by a thrust rod 2|extendinginto a recess 22 in coupled at its other end to the foot pedalC by the rod D. The piston I8 carries a packing 23 ofthe cup washer typeat its forward end, and is reduced in diameter behind its head to form35 an annular space 24 closed at its rear end by a ically through therocker to said floating piston.y

The rocker may be mounted in a liquid 'passage connecting the twocylinder bores.

The invention is more particularly applicablev to the brake system ofroad vehicles, and an embodimentgf the invention in a master cylinderunit for that purpose will now bel described with reference to theaccompanying drawings in which:

Figure l is a sectional elevation of a mastery cylinder yaccording tothe invention, the section being taken on the line I-I of Figure 2, andthe brake system to which the master cylinder is connected beingdiagrammatically indicated.

Figure 2 is a sectional plan onthe line 2 2 of Figure 1; and

Figure 3 is a sectional of Figure 1.

The embodiment oi the invention described is for the operation of brakeson a four-wheeled plan on the line 3 3 second packing 25. The piston isurged by a spring 26 inside the cylinder away from the connected' endsof the vtwo cylinders, and is limited in its movement in that directionby a circlip 21 .-40 i'n the end of the cylinder bore. In the auxiliarybore A3 is tted a oating piston 28 having an outwardly facing cup washerpacking 3| at each 'end, and having a central part of reduced diameterto form-an annular space 32. This piston is urged by a spring' 33against a suitable stop 3B in the end'of its cylinder which communicateswith the main cylinder 2.

In the cavity I3 of the cover plate I2 which connects the two cylinderbores 2 and 3 is mounted a rocker 35 comprising a lever mounted betweenlts ends on a pin 36 fitting in two notches 3i in the sides of thecavity I3, and held therein by the end face of the main casting. Anabutment 28 is carried by the main piston I0 and is '55 adapted toengage one end of the rocker 35 after etiher a left hand or face,v whichis not the case a predetermined stroke of the main piston.

abutment 4I on the floating piston engages the other end of the rocker35, this abutment 4I being in engagement with-or only very slightlyspaced from the rocker V35 when the iioating `piston Vis fullyretracted.

The usual provision spaces in front of 'the two pistons I3 and 28 to beconnected to the' reservoir spaces 6 and 1 when the pistons are fullyretracted, by means of the small apertures 42, 43 in the cylinder walls,

these apertures being covered by the initial movement of the pistoncups. The annular spaces 24, 32. around the pistons are permanently connected to the reservoir spaces by larger ports 44 and 45. -In the outletfrom the connecting cavity I3 and the outlet 4 from theV auxiliarycylinder 3 are provided two-way valves 46 and-41 which permit freepassage of liquid o ut of the cylinders, but permitreturn ilow only whenthe pressure in the pipe lines exceeds a small predetermined amount, sothat a slight pressure is always maintained in the pipelines.

is made foi-.the cylinder It is to be understood vthat the abovedescribed embodiments of my invention are for the purpose ofillustration only and various changes may be made therein withoutdeparting from the spirit.' and scope of the invention.

lI claim:

1. A master lcylinder unit, comprising a main cylinder bore, a pistontherein, an auxiliary bore, a floating piston therein, a plurality ofmotor units one of said units being connected to the main bore andaseparate un'it being connected to the auxiliary bore, an end coversecured to the end f the master cylinder unit and having a v liquidpassage therethrough connecting the main -and auxiliary bores, andmechanical means adapted to at times connect the main and auxiliarypistons, said, means including a rocker mounted inthe aforesaid liquidpassage connecting the bores.

I'hese valves consist of a metal cup-shaped I member 43 urged by aspring 5I against a packing ring 52,l and a rubber cup member 53 fittedinsidethe metal cup 43, the skirt of the cup 53 covering aseries ofapertures 54, in the wall of the metal cupl 43.- Liquid can thus passfreely out of the master 'cylinderunit by pushing aside the skirt of thecup 53, but cannot return thereto except by lifting the cup 43- from thering 52 l against the spring 5I. A pressure is therefore alwaysmaintained in the pipelines, this pressure being equal to the load ofthe springs 5 I From the outlet from the connecting cavity I3 betweenthe cylinders 2 and 3, a pipe line extends to the motor cylinders B, Boperating the shoes or equivalent members of the rear brakes A, A, andfrom the outlet`4 from the auxiliary cylinder 3 extends a pipe line tothe `motor cylinders B1, B1 operating the shoes-or equivay lent membersof the front brakes A1, A1..

Pressure on the pedal C causes the main piston I3 to move forward in itscylinder 2, forcing liquid into the pipe line leading to-the rear brakesA, A, and also forcing liquid through the connecting'cavit'y I3 intotheauxiliary cylinder 3,

where it causes the floating piston 23 to move in the opposite directionto the main piston I3, and expel liquid to the motor cylinders B1, B1,of the front, brakes. All the. brakes are thus applied with exactlyequal pressure.

Should the rear brake system. fail, due to breakage of a pipe line orfailure of a packing member, and liquid leak away, the main piston I3when operated, moves Iorward'until the abutment 33 thereon strikes therocker 35 and turns the rocker about. its pivot 36 mechanically tooperate the floating Piston 23, through its abutment member 4I. Shouldfailure take place in thev front brake system, the floating piston 23moved forward'until it strikes an abutment 55, and further movement ofthe main pistoncreates pressure in the rear brakes.

The master cylinder unit according to the present invention has theadvantages over the corresponding form of master cylinder having onlyv asingle bore, that for a given stroke 'it is shorter lin length andvcanbe arranged with both outlets at the ends, so that it-can be secured toa right hand Vsupporting if one outlet"is in the side of the cylinder,as in the single bore type cylinder. e

sage in the end cover, the said notches beingclosed' by lthe adjacentface of the main body of the cylinder unit.

3. A master cylinder unit for a liquid pressure powertransmission-system, comprising a main cylinder bore, a motor unit, aconduit connecting said main cylinder bore to said motor unit,

an auxiliary cylinder bore in parallel lrelation to the main bore, asecond motor unit, a conduit connecting said auxiliary bore to saidsecond .motor unit, an externally operable piston in the main'bore, anda floating piston in said auxiliary bore, the main piston and thefloating piston delivering liquid through said conduits to the first andsecond motor units respectively,

hydraulic means for actuating the floating pisf ton in response toactuation of theexternally operable piston, and mechanical means forvactuating the floating piston in response to actuation of thevexternally operable piston, said me- .chanicalmeans including a rockermounted in a liquid lpassage connecting the cylinder bores.

4. A master -cylinder unit for a liquid pressurel power transmissionsystem, comprising a main cylinder bore, a motor unit, a conduitconnecting -said main cylinder bore to said motor unit,

an auxiliary cylinder bore in parallel relation to the main bore, asecond motor unit, a conduit connecting said auxiliary bore to said-second motor unit, an externally operable piston in ythe main bore, anda floating pistonin said auxiliary bore, the main piston and theiioating pistc-n delivering liquid through said conduits to the firstand second motor units respectively, hydraulic means for actuating thefloating piston in response to actuation of the externallyoperablepiston, said hydraulic means including pressure,liquid and-achamber .therefor connected to both the main and auxiliaryV bores, andmechanical means for actuating the floating piston in response toactuation of the externally operable piston, said mechanical meansincluding a rocker mounted in the aforesaid chamber connecting lthecylinder bores.

5. A mastercylinder unit for a liquid pressure power transmissionsystem, comprising a main cylinder bore, a motor unit, aconduit'connecting said main cylinder bore to said motor unit, anauxiliary cylinder bore in parallel relation to the main bore, a secondmotor unit, a conduit connecting said auxiliary bore to said secondmctor unit, an externally operable piston in the main bore,l and afloating piston in said auxiliary lbore, the main piston and theiloating piston delivering liquid through said conduits to the ilrst andsecond motor units respectively, primary means for actuating theiloating piston in response to actuation of the externally operablepiston, said primary means including pressure liquid and an. end platefor the master cylinder unit -having a iluid passage therein connectingsaid bores. and mechanical means fory actuating the floating piston inresponse to actuation of the externally operable piston.

6. A master cylinder unit for a liquid pressure power transmissionsystem, comprising a main cylinder bore, a motor unit. a conduitconnecting said main cylinder bore to said motor unit. an auxiliarycylinder bore in parallel relation to the main bore, a second motorunit, a conduit connecting said auxiliary bore to said second lmotorunit, an externally operable piston in the main bore, and a ioatingpiston in said auxiliary bora-the main piston and the oating pistondelivering liquid through said conduits to the rst and second motorunits respectively, primary means for actuating the oating piston inresponse to actuation oi' the externally operable piston, said primarymeans including pressure' liquid and an end plate for the mastercylinder the main bore and a separate unit being connected to .theauxiliary bore, an end cover secured to the end of the master cylinderunit and havl .ing a liquid passage therethrough connecting the main andauxiliary bores, the said end cover carrying also the outlet connectionfrom the main cylinder bore, and means for mechanically connecting themain and auxiliary pistons including a rocker mounted in the liquidpasasge connecting the bores.

8. In a uid pressure system having a plurality of motor units, a mastercylinder unit comprising a main cylinder bore, a main piston therein, anauxiliary bore, an auxiliary piston therein, a connection between one ofthe motor units and the main bore, a connection between a separate unitand the auxiliary bore, hydraulic means' for actuating the auxiliarypiston in response to actuation of the main piston, and mechanical meansfor actuating the auxiliary piston in response to actuation of `the mainpiston, said mechanical means including a rocker mounted in a liquidpassage connecting the cylinder bores. r

l GEO y wat ROBmT GERGH GATES.,

